With the new version of GNOME came a new version of app-misc/tracker which is required, but it's causing a lot of grief for users. User will experience really high CPU usage as it spawns a lot processes and soon user will not be able to open up anything.

So in the directory /etc/xdg/autostart/ is where the trackers get started, you can simple remove all the tracker-* files. You will need to be root of course: